In an image forming apparatus, density reproducibility for faithfully reproducing the density of an image varies as a result of a developing performance of a developing unit. The developing performance of the developing unit is often deteriorated as a result of, for instance, repeated use of the image forming apparatus. Accordingly, some image forming apparatuses perform density correction processing at a predetermined timing. Related art density correction processing is performed by means of transferring a pattern consisting of a plurality of density marks of different densities onto, for example, a recording medium. A density sensor then detects the density of the thus-transferred pattern and adjusts densities of respective stages in accordance with results of the detection, thereby correcting the densities.
Japanese Patent Application JP-A-2001-309178 describes a related art technique intended for preventing excessive consumption of toner, or the like. According to the related art technique, during density processing, a simple pattern having a comparatively-smaller number of density marks is transferred onto a recording medium, and the density of the simple pattern is detected. The density of the simple pattern is compared to a previous density correction. If the density has changed only minimally, no action is taken. On the other hand, if the density has changed drastically as compared with the previously acquired density correction, a detailed pattern that is larger than the simple pattern in terms of the number of density marks is transferred onto the recording medium, and density correction then is performed in accordance with the detailed pattern.
However, the related art technique described by Japanese Patent Application No. JP-A-2001-309178 has some disadvantages. The related art technique requires many steps. This means the related art technique takes much time to complete, thus reducing the printing efficiency. Also, even when there is a high probability of a great change having arisen in density, processing pertaining to a plurality of steps including transferring a simple pattern, detecting the density of the simple pattern, transferring a detailed pattern, and detecting the density of the detailed pattern is performed indiscriminately, so that density correction processing is inefficient.